Let me just do that for my raspberry pi.
Looks like I need Certbot for Debian Stretch...
Err... need to do something about backports...
Now we have to Dick about with 'clarity' of the instructions. Dick Dick Dick..
sudo apt-get update
Reading package lists... Done
W: GPG error: http://ftp.debian.org/debian stretch-backports InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 8B48AD6246925553 NO_PUBKEY 7638D0442B90D010
W: The repository 'http://ftp.debian.org/debian stretch-backports InRelease' is not signed.
N: Data from such a repository can't be authenticated and is therefore potentially dangerous to use.
N: See apt-secure(8) manpage for repository creation and user configuration details.
Looks like that is fucked then.
LetsEncrypt - - - - LetsNotBother
... and don't give me no PEBCAK.
I worked out your stupid instructions and it fell over.
... and don't tell me the fault lies with Debian or RPi
If you tell me to use someone else's shit to use your shit you better make sure the other shit works with your shit,,, and my shit.
You may consider this to be my bug report.
FFS. Falls over on a Public Key Error.